Evaluation of neotectonic signatures and sequencing of morphotectonic events in the badlands of the Mandakini River watershed, Chitrakoot, India

The present study aims at deciphering the morphometric neotectonic features in the badland affected part of the Mandakini River watershed of Chitrakoot, India. The study attempts to decipher the relative time sequencing of the morphotectonic events based on certain assumptions. Badlands are essentially erosive systems that result due to some critical combination of multiple factors such as a change in rainfall pattern, deterioration of soil properties, overgrazing history, changes in land use and land cover, changes in groundwater conditions, etc. and may or not have additional impetus due to tectonic events in their growth. The thin layer of sediments with variable thickness showing active badlands in the study area overlies the southernmost part of the Faizabad Ridge, which has a subsurface horst formation. With the assistance of remote sensing and GIS, numerous morphotectonic parameters have been determined. The result shows that the less elongated (Re = 0.7) shape of the Mandakini River watershed, Hypsometric integral (HI = 0.48), and basin shape index (Bs = 1.6), and the windy channel are indicative of moderately active tectonism in the watershed. Although the watershed is more or less symmetrical in some parts, the basin asymmetry factor (AF) is 55.24, which again indicates there is a partial impact of low active tectonics on the watershed under the study area. Sub-watersheds at the third order-level show significant variations of these morphotectonic indicator parameters observed through the sub-watersheds of the study area. In this regard, it is also of significant consideration that the spatial orientations of several sub-watershed show strong discords from the general orientations of the rest of the sub-watersheds at the third-order level, and as such, they occur as morphometric 'inliers' in the current scheme of the current drainage processes. Continuous, uninterrupted geomorphic processes cannot account for this discord, and in the absence of any significant anthropogenic interference, these could only be correlated to aggravating impacts of neotectonics interventions. On the basis of significant values of the morphometric parameters indicative of neotectonism and spatial discord of the sub-watershed, a division of zones has been attempted here, showing a degree of neotectonic interference during the sustained erosive phase of badlands formations. The values are found to be ranging from High Tectonic to Low tectonic signatures of different tectonic activity phases. The tectonic events have been classified in the GIS environment, and the spatial signatures of tectonic events, namely the High Tectonic Activity Phase (HTAP), Moderate Tectonic Activity Phase (MTAP), and Low Tectonic Activity Phase (LTAP), have been deciphered. Finally, the present work offers assumptions for sequencing the events.